Advice needed on treatment of Efflorescence.

I have been living in my present house for around 3 1/2 years and I have a real problem with efflorescence on every downstairs wall except the adjoining wall with next door (apart from a chimney breast on this wall). The house had a damp course done around 6-7 years ago, I called in the company that did the course as it was still under warranty and they advised me that they had already visited the house when the previous owner had called them in for the same problem and found that the damp proofing was OK and that the efflorescence would eventually go away over time if I just kept removing it from the surface.
All of the efflorescence occurs in the lower third of each wall and ranges from isolated patches on some walls to almost covering others. There is no obvious sign of damp in and around the affected areas.
i'm at the stage now where the walls look a total mess, the plaster in a lot of places needs to be replaced so I am planning on taking it all off back to the brickwork and having it replastered. What I want to know is what would be the best way to prevent the efflorescence from coming back?

It sounds like they've used a lightweight undercoat plaster that is very hygroscopic. They should have used sand and cement render with a waterproofer added.

Thanks Joe.
Delayed follow-up due to knackered Laptop
I'm going to get a plasterer in to do the worst bits where the whole wall needs re-doing but I'd like to tackle some of the small isolated patches on the other walls myself.
Can anyone tell me exactly what I need and and the ratio's for the render/waterproofer mix, along with anything else I need to consider?
Thanks.

Hi MH,
As joe-90 rightly said,a coat of cement render on a wall, with a waterproofer admix in, will put a barrier between any salts etc that will come through some modern day lightweight gypsum plasters, from the brickwork.Even a "good" scratch-coat of 4-1 sand and cement with a waterproofer in, will work perfectly.The only thing you would have to watch is that when you scratch it,don't go too deep with the scratcher,you don't want to hear the sound of the scratcher on the bricks underneath.That is why I said a "good" scratch-coat.The waterproofer that I use and would recommend is "EVOPLAST".It comes in a small, plastic 5Ltr.container,and is made by Evo-Stik. It would cost around £10-£12 ish.There are larger quantities available also.The beauty of this product is the easy to understand ratio, "1 part Evoplast to 30 parts water", all the time,you can't go wrong,whether you measure with an egg-cup or a bucket.Don't exceed the ratio stated.It is not recommended for laying bricks or blocks,or for use in concrete.This product is also a plasticiser.Hope that is of some use.

Roughcaster.

Thanks Roughcaster, that's exactly what I needed.

Hi guys,

My builders were pouring a reinforced concrete beam and I asked them to put in a waterproofer. When I came home from work i saw they had put in Evoplast and in a higher ratio than the product recommends ie. about 20 parts water to 1 part Evoplast. Evoplast is not recommended for structural concrete and the ratio they used was too high. What are the effects likely to be on the concrete.